1. Field of the Invention
The present invention relates to a photovoltaic device and a method of fabricating the same. More particularly, it relates to a method of fabricating a three-dimensionally shaped photovoltaic device having three-dimensionally arranged photovoltaic elements.
2. Description of the Background Art
FIG. 13 is a sectional view showing an exemplary module structure of a conventional photovoltaic device. A plurality of photovoltaic elements 3, which are separated from one another, are provided on a substrate 1, with electrode films 2 provided between the substrate 1 and the photovoltaic elements 3.
Electrode films 4 are provided on the photovoltaic elements 3. Wires 5 connect the electrode films 4 and 2 with each other between adjacent ones of the photovoltaic elements 3, thereby connecting the photovoltaic elements 3 in series with each other.
FIG. 14 is a side elevational view showing another exemplary module structure of a conventional photovoltaic device. An electrode 9 is provided on a first end of a photovoltaic element 6, while in turn a second end of the photovoltaic element 6 is connected with a first end of a photovoltaic element 7, and a second end of the photovoltaic element 7 is brought into contact with a first end of a photovoltaic element 8, of which a second end is provided with an electrode 10. In this manner, the photovoltaic elements 6, 7, and 8 are connected in series with each other.
However, such conventional photovoltaic devices require complicated fabrication steps, for example for wire bonding between the electrodes and for contact/fixation at the ends of the photovoltaic elements.
While it is necessary to connect a number of photovoltaic elements having small areas in series with each other in order to generate high-voltage power in a given area, it is also difficult to connect such photovoltaic elements having small areas with each other by means of the conventional connection structures.
FIGS. 30 to 32 are perspective views showing an exemplary method of fabricating a conventional three-dimensional shape photovoltaic device. This three-dimensional shape photovoltaic device is adapted to be arranged on a micromachine or the like. A photovoltaic device having such a three-dimensional shape is restricted to a thin film of an amorphous semiconductor or the like because it is generally difficult to form such a device from a crystalline semiconductor film. As shown in FIG. 30, a substrate 41 having a final three-dimensional shape is first prepared. A plurality of such substrates 41 are combined with each other to attain a truncated conical shape, in order to make a three-dimensional shape photovoltaic device finally having such a truncated conical shape.
Then, a photovoltaic element layer 42 having a p-n junction is formed on the overall surface of the substrate 41, as shown in FIG. 31.
Then, prescribed portions of the photovoltaic element layer 42 are irradiated with an energy beam 44 such as a laser beam to define divided portions 43, so that the photovoltaic element layer 42 is separated into a plurality of photovoltaic elements separated from one another along the divided portions 43.
After the photovoltaic element layer 42 is separated in the aforementioned manner, the respective photovoltaic elements are wired to be connected in series with each other.
FIG. 33 is a perspective view showing a truncated conical photovoltaic device 45 which has been formed by combining a plurality of the aforementioned photovoltaic elements with each other and which is carried or mounted on a micromachine 46. The micromachine 46 carrying such a photovoltaic device 45 can be introduced into a tube 47 as shown in FIG. 33, for example, whereby the micromachine 46 can advance itself through the tube 47. In this case, a driving unit which can move on an inner wall of the tube 47 is mounted on the micromachine 46, and power is generated in the photovoltaic device 45 which is irradiated with light 48. Thus, the micromachine 46 moves in the tube 47 by means of the power generated on board the machine 46 in the photovoltaic device 45.
However, it is difficult to fabricate a three-dimensional shape photovoltaic device by such a conventional method, because it is necessary to form the photovoltaic element layer on the substrate having a three-dimensional shape. Further, it is impossible to fabricate such a photovoltaic device having excellent photoelectric conversion characteristics. In addition, the fabrication steps are complicated, because it is necessary to separate the photovoltaic element layer after it is formed and to connect wires to the separated photovoltaic elements.